Step 1: Prepare the Beef Filling

1. Heat olive oil in a large skillet over medium heat. Add the chopped onion and sauté for 3-4 minutes until translucent.
2. Stir in minced garlic and cook for another 30 seconds until fragrant.
3. Add ground beef to the skillet and break it up with a wooden spoon. Cook until the beef is browned and no longer pink, about 5-7 minutes. Drain any excess fat.
4. Season the beef mixture with chili powder, ground cumin, smoked paprika, dried oregano, salt, and black pepper. Stir well to coat the beef with the spices.
5. Mix in the black beans and diced green chilies. Cook for another 2-3 minutes, allowing the flavors to meld together. Remove from heat.

Step 2: Assemble the Casserole

1. Preheat your oven to 375°F (190°C).
2. Spread a thin layer of enchilada sauce (about ½ cup) at the bottom of a 9×13-inch baking dish.
3. Arrange a layer of quartered corn tortillas over the sauce, covering the bottom of the dish.
4. Spoon half of the beef mixture over the tortillas and spread evenly.
5. Drizzle with ¾ cup of enchilada sauce and sprinkle with 1 ½ cups of shredded cheese.
6. Repeat the layering process: tortillas, the remaining beef mixture, another ¾ cup of enchilada sauce, and 1 ½ cups of cheese.
7. Top with a final layer of tortillas, spread the remaining enchilada sauce over them, and finish with the last of the cheese.

Step 3: Bake the Casserole

1. Cover the baking dish with aluminum foil and bake for 20 minutes.
2. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.

Step 4: Prepare the Tortilla Strips

1. To make crispy tortilla strips, slice additional corn tortillas into thin strips.
2. Heat a small amount of oil in a skillet over medium heat. Fry the tortilla strips in batches until crispy, about 1-2 minutes per batch. Drain on paper towels and set aside.

Step 5: Serve and Garnish

1. Let the casserole cool for 5-10 minutes before slicing. This helps the layers set.
2. Spoon dollops of sour cream over the casserole, sprinkle with crushed tortilla strips, and garnish with chopped cilantro.
3. Add optional toppings like sliced avocado, fresh lime wedges, or jalapeño slices for extra flavor.